Since 2014, the global lithium ion battery industry has undergone enormous changes. Mobile digital type lithium ion battery industry entered a low-speed growth phase, while power type lithium ion battery industry showed a continuous spurt. Currently commercial lithium ion battery cathode materials are mainly cobalt oxide (LiCoO2) and lithium-cobalt-nickel-manganese cathode material of a layered structure, and lithium iron phosphate (LiFePO4) of a olivine-type structure. LiCoO2 material has a low specific capacity (140 mAh/g) and cobalt resources are scarce, and the price of LiCoO2 material is high and the safety of which is poor. All the reasons above limited the application of the LiCoO2 material in the power battery. Electric vehicles require lithium ion battery with a higher energy density, a better thermal stability, a better cycle performance and consistency. However, LiFePO4 can not fully meet demands of power lithium ion battery due to large differences among preparation batches, low volume energy density and fast weakening performance under working conditions. Therefore, a layered lithium-nickel-cobalt-manganese cathode material with a higher reversible specific capacity (the actual reversible specific capacity can be as high as 148-190 mAh/g) and a lower price becomes the developing focus of the new generation of power battery materials.
Most of the conventional lithium-nickel-cobalt-manganese cathode material powders are secondary agglomerated particles. The existence of fragmentation of the secondary agglomerated particles during the rolling and cycling after slurry and coating, affects the dispersion uniformity of the active material and the adhesive and the conductive agent and their contact interface with the electrolytic solution, and affects the electrical performance of the battery, especially the safety performance, high temperature stability and cycling performance of battery. So the conventional lithium-nickel-cobalt-manganese cathode material can not meet the high safety requirements of electric vehicle batteries. Therefore, new lithium ion battery cathode material need to be developed.
As reported in the Chinese patent (Application No. 201410128534.2; Publication No. CN104979546A) entitled “Preparation method of single-crystal-morphology lithium ion battery ternary positive material”, the ternary precursor was prepared by co-precipitation method, and the precursor was pretreated at high temperature for pelletization, and sintered to obtain mono-crystal primary particles with good dispersibility. As reported in the Chinese patent (Application No. 201510449404.3; Publication No. CN104966833A) entitled “Positive electrode material and preparation method thereof as well as lithium ion battery containing positive electrode material”, a ternary precursor was prepared by coprecipitation method, and then the precursor, a lithium source and metal oxide were sintered, crushed, coated and tempered to produce a cathode material of super crystal structure with a smaller crystal volume change and a smaller lithium nickel mixing degree. The cathode material has excellent structural stability and the particle has a few or no grain boundaries. The patent emphasized that the cycling performance and the first charge-discharge efficiency of the lithium ion battery were improved through coating metal element. As reported in the patent (Application No. 201610119296.8; Publication No. CN105633398A) entitled “Preparation method for power type lithium ion battery positive electrode material with primary-particle-like shape”, a primary-particle-like shape cobalt source, a lithium source and an additive were mixed and sintered, and then a cobalt source was added, and the mixture was mixed and sintered to obtain the primary particle lithium cobalt oxide cathode material for power type lithium ion battery.